Computer aided contact lens design and fabrication using spline surfaces

Abstract

A method of computer-aided contact lens design and fabrication uses spline-based mathematical surfaces without restrictions of rotational symmetry. The spline encompasses any piecewise function with any associated constraints of smoothness or continuity. The method comprises some or all of the following steps: data acquisition, three-dimensional mathematical surface model construction, posterior surface description, ray tracing for anterior surface, and peripheral edge system (PES) design. The result is a mathematical or algorithmic description of a contact lens. Based on the more powerful mathematical representation of splines, these contact lenses can have posterior surfaces that provide a good fit to corneas having complicated shapes. This enables the design and fabrication of lenses (including soft lenses) with good optics for irregularly shaped corneas.

Description

This invention relates generally to the design and fabrication of contact lenses, and in particular to a method using spline-based mathematical surfaces without restrictions of rotational symmetry.Besides the obvious cosmetic aspect, contact lenses generally offer improved visual acuity compared to spectacles. In some cases, the difference is dramatic. For example, in the case of the corneal pathology of keratoconus (a corneal condition in which there is local region of high curvature), contact lenses can often succeed in providing excellent visual acuity (perhaps 20 / 20 using the standard Snellen eye chart) whereas spectacles are not able to provide more than a minor improvement over the uncorrected vision. In addition to improved visual acuity, contact lenses are also indicated for other diverse purposes, such as a medicine delivery system or as a "bandage" for protection of the cornea after erosion, trauma, or surgery.Current contact lenses have shapes formed from relatively simpl...

AI Technical Summary

Problems solved by technology

Furthermore, Ducharme does not address the determination of the optics for the lens in the case of a spline-based design.

Although he mentions thickness, he does not provide any information that would enable someone to design a lens to achieve desired optics.

This lack of mathematical model results in a representation that is unnecessarily large and inefficient.

Note that even a combination of these prior-art references does not provide the physical features of the present application.

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